Known in the art is an internal combustion engine which arranges a particulate filter for trapping particulate matter which is contained in exhaust gas in an exhaust passage. As a result, the quantity of particulate matter which is discharged into the atmosphere is suppressed. In this regard, if the quantity of particulate matter on the particulate filter becomes greater, the pressure loss of the particulate filter will gradually become greater. As a result, the engine output is liable to drop. Therefore, known in the art is an internal combustion engine which performs control for removing PM which removes particulate matter from the particulate filter. If doing this, an increase in the pressure loss of the particulate filter due to the particulate matter is suppressed.
In this regard, exhaust gas contains noncombustible ingredients called “ash”. This ash is trapped together with the particulate matter at the particulate filter. In this regard, even if control for removing PM is performed, the ash will not burn or vaporize, but will remain on the particulate filter. For this reason, as the engine operating time becomes longer, the quantity of the ash which is trapped on the particulate filter will gradually increase and the pressure loss of the particulate filter will gradually become larger. As a result, even if control for removing PM is repeatedly performed, the engine output is liable to drop.
Therefore, known in the art is an internal combustion engine which causes the exhaust to pulsate to generate a flow of exhaust gas which flows in reverse inside the particulate filter and thereby makes the ash separate from the particulate filter (see PLT 1).